DIYARBAKIR, Turkey, March 18 (Reuters) - Turkish police swept the biggest city in the mainly Kurdish southeast collecting old tyres on Monday, in a bid to prevent their thick black smoke polluting a traditional festival.

Kurds in Turkey celebrate spring's arrival with a festival in which young men beat drums and leap over large bonfires. The ancient rite is also marked in Iran and Central Asia.

But Turkish officials this year are threatening fines of up to 714 million Turkish lira ($530) for those who burn tyres and spread heavy black smoke over the city.

"People want to celebrate in peace, not through burning tyres," one local official said.

The build-up to the festival has been marked by traditional sparring over its name -- known to the Kurds as "Newroz" and "Nevruz" in Turkish.

The People's Democracy Party (HADEP), which runs the Diyarbakir municipality, said on Monday it had refiled its application to hold the festivities on March 21, removing the Kurdish spelling, after a request from police.

"We re-applied in the form the police asked," a HADEP official, who asked not to be named, told Reuters.

Turkish has no letter W and does not recognise Kurdish as a language of officialdom.

The festival has long been a focus of Kurdish nationalist aspirations.

Much of the southeast region is covered by an emergency rule administration with powers to limit public gatherings.

The authority was set up in response to an armed Kurdish separatist insurgency that has cost more than 30,000 lives since 1984. Fighting has died down in recent years and the separatist rebels say they now prefer politics to the gun.

Turkey has eased restrictions on the spring festival in recent years.